What is voltage to frequency converters

Frequency converters and frequency converters simply explained

What exactly is a frequency converter?

A frequency converter is a machine for converting a voltage. As a rule, an electrical converter consists of a rectifier and an inverter. The rectifier supplies a direct current intermediate circuit, which the inverter uses. This is the only way to convert the current into a converted voltage. There are generally three types of frequency converters:

  • Asynchronous frequency converters
  • Synchronous frequency converters
  • Frequency converter with commutator

Asynchronous frequency converters are used to operate three-phase motors at higher speeds. A three-phase asynchronous motor and a mechanically coupled slip-ring motor are installed in them. The asynchronous frequency converter is connected to the mains with the aid of stator windings and a switch. The rotor voltage ranges from 42 to 500 volts. The mains current generates a rotating magnetic field. This creates an alternating voltage that the rotor windings pass on to the slip rings. This type of frequency converter is mainly used as a high-speed frequency converter for driving high-speed induction motors at high speeds. Synchronous frequency converters are similar to asynchronous frequency converters, with the exception that the motor is a three-phase synchronous motor. In the case of smaller machines, a reluctance motor is installed instead. Frequency converters with commutators are used to convert low-frequency alternating voltages. They drive slowly moving machines. A variable resistor is used here. A rotating field is created and the speed corresponds to the slip frequency. A collector absorbs the electrical energy.

In which machines are frequency converters installed?

Frequency converters are used to drive a wide variety of drive technology. These include:

  • Three-phase motors
  • pump
  • Air conditioners
  • Drives in heavy industry
  • Drives in the textile industry and the sugar industry

The last two points mainly relate to frequency converters with commutators. Due to the high maintenance requirements and the complex structure, they can no longer be found in many companies today. In the meantime, electronic frequency converters are mostly used instead of frequency converters.

What is a frequency converter?

A frequency converter is a power converter that changes an alternating voltage so that it can be used by electrical machines. To do this, the frequency converter changes the frequency and the amplitude in the AC voltage. It usually consists of a rectifier and an inverter. A capacitor in the intermediate circuit smooths the DC voltage and the components. Frequency converters are used to control and supply electric motors. They generate variable alternating voltages and do not work with a fixed frequency or voltage amplitude. A general distinction is made between indirect static frequency converters and direct frequency converters. Indirect static frequency converters use controlled and uncontrolled bridges as rectifiers. Controlled bridges can be transistors or switching thyristors, for example. The intermediate circuit in the frequency converter consists of a capacitor and the inductances. Frequency converters usually have components that convert excess energy into heat. Direct converters are also called matrix converters. You do not need an intermediate circuit. At the same time, they are dependent on an uninterrupted supply of energy. They can work in bridges and are used in elevators, among other things.

What are the areas of application of frequency converters?

Frequency converters are used in a variety of industries in a wide variety of sectors. They are needed where there is a fixed speed, because the alternating voltage network supplies a fixed voltage. They are used to drive machines such as:

  • pump
  • Electric railways
  • Manufacturing machines
  • Ventilation
  • transport
  • Servo drives
  • Cranes
  • Lifting systems

Depending on the areas of application, different types of frequency converters are used.

What are the differences in speed?

With a frequency converter, the mechanical speed is just as high as that of the electric motor. This is due to the tight coupling. Frequency converters, on the other hand, can switch continuously between several speeds. The bandwidth ranges from zero to the nominal speed of the network frequency.

Why do you have to convert the voltage?

The voltage is the driving force for the flow of current - without voltage there is no current. In batteries and accumulators, it is chemical processes that generate electrical voltage. Many machines use a direct current as a voltage source, while others rely on an alternating current. Alternating current is characterized by the fact that the polarity changes periodically and the voltage value changes constantly. Everyday electronic objects get along with the normal alternating current of the power grid. This supplies a constant alternating voltage. However, certain machines and motors require variable alternating voltages in order to be able to switch the speed and torque, for example. Frequency converters and frequency converters have the task of adapting this alternating voltage from the grid. As a result, three-phase motors are not throttled in performance and can be controlled in a targeted manner.

What accessories are there for frequency converters?

There are various accessories and other products on the market for the use of frequency converters, such as shielded cables, control elements, sinusoidal filters, braking resistors or line filters. There are also portable frequency converters. This can be used to operate external vibrators, high-frequency internal vibrator systems and vibration plates for compaction during construction. The adjustment of the speed is important for the configurations of the high-frequency internal vibrator systems.